In the next MPh the Berserk unit will charge to/towards the Location where it last saw a Known enemy unit. Once there - if no Known enemy unit is in LOS, it returns to normal.
If the broken unit is the last Known enemy unit that the berserked har LOS to come its next MPh, it will "charge" its own Location. Basically doing nothing the MPh and returning to normal after that.
Unless the broken unit manages to not be Known (I don't think that's possible), the Berserker will charge it no matter what, as it will always be the closest Known enemy unit.
But I don't think this was the original question. If the Berserker charges a broken unit and enters its hex, the broken unit is still not in Melee in the next RtPh, and will be able to rout away - its first hex is allowed to be adjacent to the Berserker because it is leaving its location. But it won't be able to remain in the Berserker's location.
But in a situation where a Berserker is in a broken enemy unit's Location (and not in Melee) at the start of its MPh, I would say it takes a 0MF charge (with no possible DFF).